Many medical devices, for example, medical electrical leads and drug delivery catheters, include elongate bodies facilitating therapy delivery and/or diagnostic sensing; the bodies often include lumens extending along a longitudinal axis thereof. Such a lumen may provide a passageway for a stylet or guidewire that helps to guide the device to a target site within a body of a patient, for example, within a chamber of the heart. In recent years, the space used for guidewire/stylet lumens within elongate bodies of many medical devices has either been eliminated, to downsize the device bodies, or used for other purposes, for example, for the routing of one or more additional lead wires that add functionality to the device. Delivery catheters have been developed to guide these elongate medical devices, which do not have stylet/guidewire lumens, to a target implant site, and these devices are sometimes designated as “catheter-delivered” devices.
In order to implant the elongate body of a medical device in the venous system, for example, a right atrium, a right ventricle or a coronary sinus, an implanting physician first obtains venous access by inserting an introducer sheath into an access site, for example, in the cephalic, sub-clavian, or axillary vein, according to methods known to those skilled in the art. The implanter may then insert a catheter delivered medical device within a delivery catheter lumen, either before or after inserting the delivery catheter into the venous system through the introducer sheath. Once the delivery catheter has been steered or directed to a target implant site within the venous system, the implanter advances the medical device through the catheter lumen and out through a distal tip to fix a distal end of the device at the site. After the medical device is fixed, the implanter typically removes the introducer sheath and/or the catheter from the venous system, typically by splitting a wall of each to peel, or slit them away from around a proximal portion of the medical device body that extends out from the venous system. In some cases, after removing the introducer sheath and catheter, the implanter discovers that the distal end of the medical device has become dislodged, or that the distal end needs to be repositioned to provide better therapy delivery and/or diagnostic sensing. Since the catheter delivered device does not include a stylet or guidewire lumen, there is a need to re-gain venous access around the device, in order that another delivery catheter can be inserted into the venous system to reposition the device. Similar situations may arise for elongate devices implanted, via a delivery catheter, within other portions of a patient's body outside the venous system, for example, for epicardially implanted devices.